The present invention relates to an optical signal control device that may be used for purposes such as, for example, optical switching (an optical 2-by-2 switch), optical variable attenuation and optical variable beam splitting, although the present invention is not limited to these particular uses. The optical devices provided by the present invention do not require, although they may include, moving parts, and are more reliable, less expensive and less bulky than other types of optical devices, such as opto-mechanical switches, for example.
Optical switches are used for a variety of purposes. A 2-by-2 optical switch has two states, namely, a “cross state” and a “bar state”. A 2-by-2 switch in the bar state is shown in FIG. 1A. A 2-by-2 switch in the cross state is shown in FIG. 1B. Some 2-by-2 switches are opto-mechanical in design and include mirrors that are physically moved to cause the switch to go from the bar state shown in FIG. 1A to the cross state shown in FIG. 1B, and vice versa. Sometimes the mirrors become fixed in a certain position, which can prevent the switch from changing state. Also, such switches may not need to be switched from one state to the other for very long periods of time (e.g., many years) once they have been installed. This lack of use may cause the mirrors to become fixed in one state simply due to lack of movement. Consequently, opto-mechanical switches tend to be somewhat unreliable. They also are bulky because they use relatively large optical and mechanical components, which causes these switches to consume a large amount of space.
Optical 2-by-2 switches do exist that do not rely on movable parts, but they tend to be susceptible to optical cross talk. Accordingly, a need exists for optical signal control devices, such as 2-by-2 optical switches, for example, that do not exhibit much, if any, optical cross-talk and insertion loss, that do not require movable components and that are less bulky than other types of optical signal control devices.